How would you justify the presence of `18` elements in the `5th` period of the periodic table?

Explanation

To justify the presence of 18 elements in the 5th period of the periodic table, we need to analyze the electron configuration of the elements in this period and the orbitals that are being filled.

### Step-by-Step Solution:

1. **Identify the Orbitals in the 5th Period**:
- The 5th period of the periodic table includes elements whose electrons are filling the 5s, 4d, and 5p orbitals.

2. **Determine the Electron Capacity of Each Orbital**:
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